Assessment of fossil-free steelmaking based on direct reduction applying high-temperature electrolysis

Preventing humanity from serious impact of climate crisis requires carbon neutrality across all economic sectors, including steel industry. Although fossil-free steelmaking routes receiving increasing attention, fundamental process aspects, especially approaches towards the improvement of efficiency and flexibility, are so far not comprehensively studied. In this paper, optimized process concepts allowing for a gradual transition towards fossil-free steelmaking based on the coupling of direct reduction process, electric arc furnace and electrolysis are presented. Both a high-temperature and low-temperature electrolysis were modeled and possibilities for the integration into existing infrastructure are discussed. Various schemes for heat integration, especially when using high-temperature electrolysis, are highlighted and quantified. It is demonstrated that the considered direct reduction-based process concepts allow for a high degree of flexibility in terms of feed gas composition when partially using natural gas as a bridge technology. This allows for an implementation in the near future as well as the possibility of supplying power grid services in a renewable energy system. Furthermore, it is shown that an emission reduction potential of up to 97.8% can be achieved with a hydrogen-based process route and 99% with a syngas-based process route, respectively, provided that renewable electricity is used.